This K24 Midcareer Investigator Award application outlines of program of patient-oriented research involving the use of immunotherapy strategies for the treatment of melanoma and renal cell carcinoma (RCCA). The principal investigator, Michael B. Atkins, M.D., competed his oncology training in 1987. He is an accomplished clinical investigator in the areas of biologic therapy and has a proven track record as a mentor for fellows and junior faculty pursuing careers in cancer related clinical investigation. He has devoted much of his career to the investigation of cytokine he-based therapies for melanoma and RCCA and was a major contributor to the FDA approval of high-close IL-2 therapy for these two diseases. His more recent efforts have focused on enhancing the therapeutic index of cytokine therapy either through combinations with other cytokines or chemotherapy, administration of selective toxicity blocking agents, the use of other cytokines with more promising therapeutic profiles, or the targeting of treatment to those most likely to respond. The first part of this application, encompassing 5 Specific Aims and 7 clinical trials, deals with the latest extensions of this work. Aim 1 will use serial blood, tumor and lymph node specimens obtained from melanoma patients participating in the two Phase III Intergroup trials for Stage III or IV disease (led by Dr. Atkins) to determine the mechanisms underlying sensitivity and resistance to cytokine-based therapy. Aim 2 will examine the roles that T cell receptor and DC dysfunction play in mediating resistance to IL-2 therapy in the context of two CWG trials for patients with RCCA. Aim3 will examine the value of adding IL-2 to IL-12 therapy using strategies derived from our prior translational research studies with IL-12 alone. Aim4 will test the ability of a novel IL-2 that selectively binds the high affinity IL-2 receptor, to dissociate immune activation from toxicity. Finally, Aim5 will examine pathology material from RCCA patients on prior CWG IL-2 trials, as when is perform gene expression analysis on prospectively obtained tumor tissue from patients about to receive IL-2, in order to determine pathologic and molecular correlates or response and resistance. A second component of this application, involving 2 Aims and 3 additional clinical trials, will explore novel immunotherapy strategies aimed at overcoming tumor-specific tolerance. Two approaches that are actively being studied are vaccination with DC: tumor fusion cells (Aim 6) and non-myeloablative allogeneic stem cell transplantation (Aim 7). The ultimate goal is to combine one or both of these strategies with cytokine based treatment (incorporating the lessons learned in specific aims 1-5) to produce more effective immunotherapy approaches for these two diseases. These projects provide at least four clearly defined paths for fellows or junior faculty members to pursue patient-oriented clinical research under the guidance of clinical research and laboratory mentors. Regular meetings with Dr. Atkins, multidisciplinary conferences, focused clinical rotations, and a clinical investigation course will round out the trainee experience. Taken together, this work should determine the factors critical to the successful immunotherapy of patients with melanoma or RCCA and, at the same time, provide superb training for the next cadre of clinical investigators who will be counted on to extend this effort.